More Minutes, Fewer Steps: Hourly Associations Between Adolescent Smartphone Use and Physical Activity

Area of Science:

• Adolescent Health
• Digital Technology Use
• Physical Activity Measurement

Background:

• Many adolescents fail to meet physical activity recommendations.
• Digital technology, particularly smartphones, is often blamed for low physical activity levels due to potential time displacement.
• Existing research on the relationship between digital technology use and physical activity is inconsistent, necessitating objective measurement.

Purpose of the Study:

• To investigate hourly associations between objectively measured smartphone use and physical activity in adolescents.
• To test the displacement hypothesis, examining if time spent on smartphones reduces physical activity.
• To differentiate the effects of smartphone screen time versus phone pickups on physical activity.

Main Methods:

• Objective assessment of smartphone screen time and pickups in late adolescents (N=67).
• Objective measurement of physical activity using Fitbit-assessed step counts.
• Analysis of hourly associations between smartphone use metrics and step counts.

Main Results:

• Increased smartphone screen time was associated with decreased step counts, supporting the displacement hypothesis.
• Increased smartphone pickups were associated with increased step counts.
• The findings suggest a nuanced relationship between different types of smartphone engagement and physical activity.

Conclusions:

• Evidence supports a displacement effect for smartphone screen time on physical activity.
• Smartphone pickups do not show a displacement effect and may be associated with increased activity.
• Further research is required to understand contextual factors and individual differences influencing these associations.